Interestingly, no data support the theory that a rapid rise in temperature is a cause of febrile seizures.

About one third of all children with a first febrile seizure experience recurrent seizures.
[22] Risk factors for recurrent febrile seizures include the following
[23, 24] :

Young age at time of first febrile seizure

Relatively low fever at time of first seizure

Family history of a febrile seizure in a first-degree relative

Brief duration between fever onset and initial seizure

Multiple initial febrile seizures during same episode

Patients with all 4 risk factors have greater than 70% chance of recurrence. Patients with no risk factors have less than a 20% chance of recurrence.

Regarding vaccination and risk of febrile seizures, Administration of the first dose of MMRV vaccine at age 12-15 months carries a slight increase risk of febrile seizure (0.05%, approximately 1 in 2000), from day 5 through 12 following receipt of the vaccine. However, the risk is not higher in older children receiving the second dose of MMRV.
[25] A study by Macartney et al evaluated the risk of febrile seizures after a second dose of MMRV vaccine at 18 months. The study reported no increased risk of febrile seizures (RI, 1.08; 95% CI, 0.55-2.13) in the 5 to 12 days following MMRV vaccine given as the second MCV to toddlers.
[26]

In a Danish study, DTaP-IPV-Hib vaccination was associated with an increased risk of febrile seizures on the day of first and second vaccinations, although the absolute risk was small. A higher risk for febrile seizures was found on the day of first vaccination (hazard ratio [HR], 6.02; 95% confidence interval [CI], 2.86-12.65), as well as on the day of the second vaccination (HR, 3.94; 95% CI, 2.18-7.10), but higher risk was not seen on the day of the third vaccination (HR, 1.07; 95% CI, 0.73-1.57) when compared with the reference group. Vaccination with DTaP IPV-Hib was not associated with an increased risk of epilepsy.
[27]

In a case-series analysis of a cohort of 323,247 US children born from 2004 to 2008, Hambidge et al found that delaying the first dose of MMR or MMRV vaccine beyond the age of 15 months may more than double the risk of postvaccination seizures in the second year of life.
[28, 29]

A study by Duffy et al sought to determine whether concomitant administration of trivalent inactivated influenza vaccine (IIV3) with other vaccines affects the febrile seizure risk. The study found that the administration of IIV3 on the same day as either pneumococcal conjugate vaccine or a diphtheria-tetanus-acellular-pertussis-containing vaccine was associated with a greater risk of febrile seizure than when IIV3 was given on a separate day. However, the absolute risk of postvaccination febrile seizure with these vaccine combinations was small.
[30, 31]

Verity CM, Butler NR, Golding J. Febrile convulsions in a national cohort followed up from birth. I--Prevalence and recurrence in the first five years of life. Br Med J (Clin Res Ed). 1985 May 4. 290(6478):1307-10. [Medline].

Verity CM, Butler NR, Golding J. Febrile convulsions in a national cohort followed up from birth. II--Medical history and intellectual ability at 5 years of age. Br Med J (Clin Res Ed). 1985 May 4. 290(6478):1311-5. [Medline].

Debra Slapper, MD Physician, Southwest Washington Free Clinic System-Urgent Care; Former FEMA Physician and Military Contractor; Former Associate Professor, University of Miami, Leonard M Miller School of Medicine and University of South Florida Morsani College of Medicine